Roller guide for a vehicle-seat oscillation system having a scissor-type guide

ABSTRACT

The invention relates to a roller guide for a vehicle-seat oscillation system having a scissor-type guide, which scissor-type guide has a scissor-type cross tube which, at each of its two ends, has a respective pin as a hub, there being rotatably disposed on at least one of the pins first roller, of plastic, which runs in a U-profile running rail and which is of such a diameter that it runs with little play in the running rail. According to the invention, provision is made whereby there is rotatably disposed on the pin, between the respective end of the scissor-type cross tube, beyond which end the pin projects, and the first roller, a disc whose diameter is slightly smaller than the diameter of the first roller or a small plate whose height is slightly less than the diameter of the first roller is disposed on the pin, the hardness of the disc or of the small plate being significantly greater than the hardness of the first roller.

CROSS-REFERENCE To RELATED APPLICATION

This is a utility application that claims Priority benefit, under 35 USC§119 (a), to German Patent Application No. 102005005889.2, filed Feb. 9,2005, which application is incorporated herein by reference.

BACKGROUND

The invention relates to a roller guide for a vehicle-seat oscillationsystem having a scissor-type guide, which scissor-type guide has ascissor-type cross tube which, at each of its two ends, has a respectivepin as a hub, there being rotatably disposed on at least one of the pinsa first roller, of plastic, which runs in a U-profile running rail andwhich is of such a diameter that it runs with little play in the runningrail.

Such roller guides are sufficiently well known as vehicle seat bearingsin the case of scissor-type oscillation systems. The rollers in thiscase are produced as injection-moulded parts from a plastic. The rollersrun in metal running rails having a U-shaped profile. In the case ofheavy loading, for example in the case of a rear-end collision, theserollers frequently break. This then regularly results in relativelylarge deformations of the vehicle seat and, in some cases, asconsequential damage, even in the complete failure of individualcomponents or of the vehicle seat as a whole.

SUMMARY OF THE INVENTION

In order to avoid the disadvantages described above, the rollers arerealized as a metal part or as a plastic solid-material part, forexample as a turned part. Although this does prevent breakage of therollers, the materials and the production process are neverthelesssubstantially more expensive.

It is therefore the object of the invention to present a roller guidewhich, on the one hand, is inexpensive to produce and, on the otherhand, even in extreme situations does not lead to deformations of thevehicle seat as a result of a major deformation or possible breakage ofa roller.

The object is achieved by a roller guide having the features of claim 1.Due to the fact that, in addition to the first plastic roller, there isalso rotatably mounted on the pin a disc whose hardness is significantlygreater than the hardness of the first roller, even in the case of adeformation of the first plastic roller in the event of high loading nodeformation of the vehicle seat can occur, since the harder disc assumesthe guidance function within the running rail. In the context of thisapplication, the term hardness means the material strength. Its ratio isnormally at least 1:5. In the case of the preferred use of a plasticroller—for example having a material strength of 60 N/mm²—and of a smallsteel plate—for example having a material strength of 500 N/mm²—thisratio is between 1:8 and 1:10. The ratio may, however, be greater than1:10, depending on the materials used. The same applies if, instead ofthe disc, a small plate is used, its height being slightly less than thediameter of the first roller. In the context of this application, theterm slightly smaller diameter means that, upon compression of theroller in the case of normal operating load, the difference in the twodiameters is within the range of the deformation. Depending on thematerials, this difference lies within a range from 0.2-2.0 mm; it couldbe greater than said range, however, in the case of appropriatematerials. In this case, the small plate, as a safety element, offerseven greater safety, since it bears flat on the running rail. Providedthat the first roller is only slightly deformed-in particular, is notbroken—the disc, owing to its slightly smaller diameter, or the smallplate, owing to its slightly lesser height, is not in contact with therunning rail, such that, in this case, the running characteristics areunchanged compared with the running characteristics known from the priorart. Only in the event of a breakage or significant deformation of thefirst roller, composed of plastic, does the disc or the small plateassume the function of said first roller.

A small plate, within the meaning of the invention, is to be understoodto include both rectangular small plates and small plates of anycontour, such as, for example, a lozenge, a triangle, an n-polygon, asemicircle or an ellipse. In this connection, the height of such a smallplate—when the small plate is in the mounted position on the pin—is tobe understood to be the greatest distance between respectively twopoints on the contour face that are vertically over one another. Thewidth in this case may also be greater than the diameter of the roller,particularly if the small plate is realized as a rectangle. In order toprevent rattling, such a small plate may be coated, for example with apaint or an appropriate plastic.

An advantageous development of the invention makes provision whereby thedisc or the small plate is disposed only on that end of the scissor-typecross tube that is located on the side of an upper connection point of aseat-belt mounted on the seat. Since the loading is greater on thestated side, deformation of the first roller occurs here first, saiddeformation being taken up by the disc or by the small plate. The otherside is only affected in the case of application of a much greaterforce.

A further advantageous development of the invention makes provisionwhereby respectively a first roller and a disc or small plate aredisposed at each of the two ends. This increases the safety comparedwith the single-sided realization, since the other side is also secured.

The disc or the small plate is preferably composed of a steel. As aresult, the disc or small plate is extremely stable, and also cannot bedestroyed by high loads, such that there can be no consequential damageto the vehicle seat. Moreover, such a disc or such a small plate can beproduced very easily, for example by a simple stamping process.

A further advantageous development of the invention makes provisionwhereby there is rotatably disposed on the pin, between the end of thescissor-type cross tube and the disc or small plate, a second roller, ofplastic, whose diameter is slightly greater than the diameter of thedisc or the height of the small plate respectively. As a result, even inthe case of a major deformation or a breakage of the oneroller—irrespective of whether it be the first or the second roller—alonger service life of the roller guide is achieved, since said rollerguide can still be moved on the remaining roller within the runningrail. Only if both rollers are defective does the disc or small plate ofsignificantly harder material again become operative and assume thefunction of the two rollers, such that there is no consequential damageto the vehicle seat in any case.

A further advantageous development of the invention makes provisionwhereby the disc or the small plate bears fully on the first roller andbears flat on the end of the scissor-type cross tube, or fully on thesecond roller. It is thereby possible for the disc or the small plate tobe realized as a very thin disc or small plate, since buckling of thedisc or small plate is prevented by their bearing on the first rollerand on the second roller, or on the end of the scissor-type cross tube.In this case, the thickness of the disc or small plate may even bereduced to such an extent that it is in the range from 1 to 5 mm, beingpreferably 2 mm in the case of an embodiment in steel.

A further advantageous development of the invention makes provisionwhereby the disc is firmly connected to one of the rollers. This enablesone less part to be mounted on the hub, resulting in simplifiedassembly. For a small plate, this is also possible in the case of anappropriate contour. Thus, in the case of an n-polygon with a largenumber of sides, a close approximation to the circular form is achieved,and the small plate does not project over the roller. This would notapply in the case of a triangle, since the edge length of thetriangle—in the case of the height being only slightly less than thediameter of the roller—would be so long that the small plate wouldproject over the roller.

A further advantageous development of the invention makes provisionwhereby the disc is integrated into one of the rollers, particularly asan insert in an injection-moulded part. Such an integrated part can beproduced very easily and inexpensively with, at the same time, a highquality as a mass-produced article. The above statements in thisparagraph also apply to small plates.

The first roller and/or the second roller is preferably realized as aninjection-moulded part. The plastic parts that are known from the priorart, and that can be produced very easily and inexpensively, can thus beused for these two rollers.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantageous developments of the invention are explained morefully with reference to the two exemplary embodiments represented in thefigures, wherein:

FIG. 1 shows a partial cross-section through a first exemplaryembodiment of a roller guide according to the invention, and

FIG. 2 shows a partial cross-section through a second exemplaryembodiment of a roller guide according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The first exemplary embodiment represented in FIG. 1 shows one of thetwo end portions of a scissor-type cross tube 1 which is guided, via afirst roller 6, in a running rail 4. The realization described in thefollowing is present as one further, identical, realization at the otherend (not shown) of the scissor-type cross tube 1. Moreover, the solutionpresented may instead be realized at all bearing points of thescissor-type cross tubes 1 or, also, only at selected points, forexample at the bearing points that have to take up higher loads in thecase of an accident. The scissor-type cross tube 1 represented is partof a vehicle-seat oscillation system having a scissor-type guide, as haslong been known from the prior art. Since the exact design of thevehicle-seat oscillation system is not essential to the invention, it isnot described in greater detail in the following.

Realized at the end 2 of the scissor-type cross tube 1 is a pin 3, whichserves as a hub. Rotatably mounted on this pin 3 are two elements,namely a first roller 6 and a disc 7. In this case the disc 7 is locatedbetween the end 2 of the scissor-type cross tube 1 and the first roller6.

Both the first roller 6 and the disc 7 are disposed within the U-shapedrunning rail 4. The U-profile is so disposed that its two limbs 5 pointtowards the scissor-type cross tube 1. The running rail 4 is a deviceknown from the prior art, there being no need for more detailedreference to its design, since a person skilled in the art is familiarwith said design.

The first roller 6 is produced from plastic, as an injection-mouldedpart. It is of a diameter which is preferably slightly smaller than thedistance between the two limbs 5 of the running rail 4, such that thescissor-type cross tube 1 is guided with little friction within therunning rail 4. Apart from the disc 7 additionally mounted on the pin3—which disc 7 is described in the following in respect of both itsdesign and its functioning—the roller guide is a roller guide, wellknown from the prior art, for a vehicle-seat oscillation system having ascissor-type guide.

In the exemplary embodiment represented, the disc 7 according to theinvention is made from a steel. Since the disc 7 is of a significantlygreater hardness than the plastic of the first roller 6, breakage of theroller 6 is to a large extent prevented, since the disc 7 assumes aportion of the load. If a breakage of the roller 6 does occur, however,the disc 7 assumes the load completely, such that there is no furtherdamage to the seat. The further damage that occurs upon breakage ofrollers 6 in the case of an accident is sufficiently well known fromcrash simulations, and is not explained more fully here. In order thatthe disc 7 can take up the load, the two limbs 5 of the running railextend so far in the direction of the scissor-type cross tube 1 thatthey reach to the end 2 of said scissor-type cross tube 1. The disc 7that is rotatably disposed on the pin 3 is thus located within therunning rail 4. This design makes it possible, on the one hand, tocontinue to produce the first roller 6 in a very inexpensive manner and,at the same time, to ensure safety in the case of a breakage or majordeformation of the first roller 6 in the case of extreme loads. In thiscase, the diameter of the disc 7 is made to be slightly smaller thanthat of the first roller 6. This, in normal operation—provided that thefirst roller 6 is intact—provides for a good roller guidance—known fromthe prior art, since in this case the disc 7 is not in contact with thelimbs 5 of the running rail 4.

The disc 7 may be made very thin—in the exemplary embodimentrepresented, it has a thickness of only 2 mm—since buckling isprevented. In the exemplary embodiment represented, this is assured, inthe direction of the first roller 6—i.e. away from the scissor-typecross tube 1—in that the entire surface of the disc 7 bears on the firstroller 6. Moreover, the other surface of the disc 7 bears, in a largearea, on the end 2 of the scissor-type cross tube 1, such that bucklingin the direction of the scissor-type cross tube 1 is prevented. Such athin disc 7 can be produced very inexpensively—for example, by astamping process—but it performs its function as a protection in thecase of breakage of the first roller 6 in an excellent manner.

FIG. 2 shows a second exemplary embodiment of a roller guide accordingto the invention which, to a large extent, corresponds to the firstexemplary embodiment represented in FIG. 1. In the following, therefore,only the differences compared with the first exemplary embodiment areexplained more fully. Parts which are the same or have the same functionare given identical reference numerals.

In addition to the first roller 6, a second roller 8 is mounted on thepin 3 of the scissor-type cross tube 1. This second roller 8 is disposedbetween the steel disc 7 and the end 2 of the scissor-type cross tube 1.The second roller 8 has a diameter which is slightly greater than thatof the first roller 6. It is likewise made from a plastic, and in thiscase can also be produced very inexpensively as an injection-mouldedpart. Since the diameter of the second roller 8 is slightly greater thanthat of the first roller 6 and, at the same time, one of the two limbs 5of the running rail 4 is made shorter, in profile both rollers 6, 8 havebearing contact only on one side (the first roller 6 on the upper limb 5and the second roller 8 on the lower limb 5), facilitating the rotarymotion of the rollers 6, 8 in the case of small tolerances. This type ofroller guidance has long been known in the art, and need not beexplained further. Also, in the case of insertion of the disc 7 as asafety element in this type of roller guide, the diameter of the disc 7is slightly smaller that that of the rollers 6, 8. The length of thelimbs 5 is made such that, in the case of deformation or breakage of oneor both rollers 6, 8, the disc 7 is located within the two limbs 5 andthus takes up the occurring loads.

In an advantageous development of the invention, provision is madewhereby the disc 7 is firmly connected to the respective roller 6, 8,this facilitating assembly, since the number of parts to be assembled isthus reduced. Many known technical solutions have long been availablefor the nature of the design of the connection of the metal disc 7 tothe plastic roller 6, 8. Said solutions need not be explained here,since they are known to the specialist in the art.

Instead of the disc 7 as a safety element, it is also possible to use asmall steel plate (not shown)—particularly in the form of arectangle—that is of a height which is slightly smaller than thediameter of the rollers 6, 8. Although this small plate cannot be firmlyconnected to the rollers 6, 8, or even injection-moulded into thelatter—whereby the advantage of fewer components in not achieved—itnevertheless constitutes a flat bearing contact on the lower limb 5 ofthe running rail, resulting in improved safety. This also applies, inprinciple, to small plates of any contour.

In addition to the design of the second roller 8 with a diameter that isgreater than that of the first roller 6, the two rollers 6, 8 may alsobe realized with the same diameter.

1. Roller guide for a vehicle-seat oscillation system having ascissor-type guide, which scissor-type guide has a scissor-type crosstube which, at each of its two ends, has a respective pin as a hub,there being rotatably disposed on at least one of the pins a firstroller, of plastic, which runs in a U-profile running rail and which isof such a diameter that it runs with little play in the running rail,characterized in that there is rotatably disposed on the pin, betweenthe respective end of the scissor-type cross tube, beyond which end thepin projects, and the first roller, a disc whose diameter is slightlysmaller than the diameter of the first roller or a small plate whoseheight is slightly less than the diameter of the first roller isdisposed on the pin, the hardness of the disc or of the small platebeing significantly greater than the hardness of the first roller. 2.Roller guide according to claim 1, characterized in that the disc or thesmall plate is disposed only at that end of the scissor-type cross tubethat is located on the side of an upper connection point of a seat-beltmounted on the seat.
 3. Roller guide according to claim 1, characterizedin that respectively a first roller and a disc or small plate aredisposed at each of the two ends.
 4. Roller guide according to claim 1,claims, characterized in that the disc or the small plate is composed ofa steel.
 5. Roller guide according to claim 1, characterized in thatthere is rotatably disposed on the pin, between the end of thescissor-type cross tube and the disc or small plate, a second roller, ofplastic, whose diameter is slightly greater than the diameter of thedisc or the height of the small plate respectively.
 6. Roller guideaccording to claim 1, characterized in that the disc or the small platebears fully on the first roller and bears flat on the end of thescissor-type cross tube, or fully on the second roller.
 7. Roller guideaccording to claim 1, characterized in that the disc is firmly connectedto one of the rollers.
 8. Roller guide according to claim 7,characterized in that the disc is integrated into one of the rollers,particularly as an insert in an injection-moulded part.
 9. Roller guideaccording to claim 1, characterized in that the disc or small plate hasa thickness of 1 to 5 mm, preferably 2 mm.
 10. Roller guide according toclaim 1, characterized in that the first roller and/or the second rolleris an injection-moulded part.
 11. Roller guide according to claim 5,characterized in that the first roller and/or the second roller is aniniection-moulded part.